Fifth wheel hitches for towing a trailer behind a towing vehicle are well known in the art. Typically, fifth wheel hitches include a support frame for mounting the hitch to the towing vehicle. Usually, fifth wheel hitches are mounted within the bed of a pick-up truck. The support frame includes a pair of transverse rails that are bolted to the bed and/or frame of the truck, rail assemblies that are releasably mounted to the transverse rails and upright assemblies mounted to the rail assemblies. A transverse cross bar typically interconnects the upright assemblies, thereby forming a head support for mounting a head assembly by means of a trunnion arrangement allowing for pivotal fore and aft movement. The head assembly includes a jaw assembly operable by means of a control handle and is specifically adapted to releasably engage and hold a kingpin of a towed vehicle.
Conventional fifth wheel trailer hitches typically limit the maneuverability of a towing vehicle at low speeds and in close quarters. In particular, fifth wheel hitches typically center the kingpin of the towed vehicle substantially between the rear wheels and over the rear axle of the towing vehicle. When so mounted, very close clearance is provided between the towed vehicle and portions of the towing vehicle. Under normal towing conditions, the close clearance is sufficient to allow effective operation under speed on the open road. However, the close clearance may hinder maneuverability, especially in situations requiring tight cornering within limited space, such as, for example, the conditions found at campgrounds and some trailer parks.
In order to address the maneuvering shortcomings of conventional fifth wheel trailer hitches, various attempts at adjustable fifth wheel hitches have been made. It has been found that by temporarily moving the hitch assembly rearward in the towing vehicle, clearance between the towing vehicle and the towed vehicle is increased, thereby allowing for greater maneuverability of the towed vehicle. In one adjustable fifth wheel hitch design, the towed vehicle must be detached from the fifth wheel hitch prior to any adjustment of the fifth wheel hitch. The detachment efforts are time consuming and require precise movement of the towing vehicle. The adjustable hitches also typically require more than one person to effect the adjustment of the fifth wheel hitch. Another design utilizes low friction shoes within upright mounting members for movement on parallel guide rails. The uprights are selectively slideable along each guide rail. Each upright includes a hollow cavity for receiving a dual bar latch and a leaf spring for biasing the dual bar latch into a position to lock the uprights against slideable movement. However, the effective weight borne by the low friction shoes tends to cause binding of the shoes such that seizing may occur. The high friction between moving parts prevents easy and smooth adjustment of the fifth wheel trailer hitch. Moreover, the latching mechanism is hidden from view, thereby preventing an operator from confirming engagement of the locking mechanism to lock the adjustable portion against slideable movement.